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      1 /* ===-- udivsi3.c - Implement __udivsi3 -----------------------------------===
      2  *
      3  *                     The LLVM Compiler Infrastructure
      4  *
      5  * This file is dual licensed under the MIT and the University of Illinois Open
      6  * Source Licenses. See LICENSE.TXT for details.
      7  *
      8  * ===----------------------------------------------------------------------===
      9  *
     10  * This file implements __udivsi3 for the compiler_rt library.
     11  *
     12  * ===----------------------------------------------------------------------===
     13  */
     14 
     15 #include "int_lib.h"
     16 
     17 /* Returns: a / b */
     18 
     19 /* Translated from Figure 3-40 of The PowerPC Compiler Writer's Guide */
     20 
     21 ARM_EABI_FNALIAS(uidiv, udivsi3)
     22 
     23 /* This function should not call __divsi3! */
     24 COMPILER_RT_ABI su_int
     25 __udivsi3(su_int n, su_int d)
     26 {
     27     const unsigned n_uword_bits = sizeof(su_int) * CHAR_BIT;
     28     su_int q;
     29     su_int r;
     30     unsigned sr;
     31     /* special cases */
     32     if (d == 0)
     33         return 0; /* ?! */
     34     if (n == 0)
     35         return 0;
     36     sr = __builtin_clz(d) - __builtin_clz(n);
     37     /* 0 <= sr <= n_uword_bits - 1 or sr large */
     38     if (sr > n_uword_bits - 1)  /* d > r */
     39         return 0;
     40     if (sr == n_uword_bits - 1)  /* d == 1 */
     41         return n;
     42     ++sr;
     43     /* 1 <= sr <= n_uword_bits - 1 */
     44     /* Not a special case */
     45     q = n << (n_uword_bits - sr);
     46     r = n >> sr;
     47     su_int carry = 0;
     48     for (; sr > 0; --sr)
     49     {
     50         /* r:q = ((r:q)  << 1) | carry */
     51         r = (r << 1) | (q >> (n_uword_bits - 1));
     52         q = (q << 1) | carry;
     53         /* carry = 0;
     54          * if (r.all >= d.all)
     55          * {
     56          *      r.all -= d.all;
     57          *      carry = 1;
     58          * }
     59          */
     60         const si_int s = (si_int)(d - r - 1) >> (n_uword_bits - 1);
     61         carry = s & 1;
     62         r -= d & s;
     63     }
     64     q = (q << 1) | carry;
     65     return q;
     66 }
     67